Multipass electric heater



y 4, 1956 L. p. HYNES 2,756,320

MULTIPASS ELECTRIC HEATER Filed April 20, 1954 4 Sheets-Sheet l Je -M INYENTOR lee K H nes- July 24, 1956 L. P. HYNES MULTIPASS ELECTRIC HEATER 4 Sheets-Sheet. 3

Filed April 20, 1954 R w A e e Z ATTORNEYS.

July 24, 1956 P. HYNES MULTIPASS ELECTRIC HEATER 4 Sheets-Sheet 4 Filed April 20, 1954 INVENTOR Zea l? H nes.

MULTIPASS ELECTRIC HEATER Lee P. Hynes, I-lladdonfield, N. 1., assignor to Turbine Equipment Company, New York, N. Y., a corporation of New Jersey Application April 20, 1954, Serial No. 424,291

8 Claims. (Cl. 219-39) The present invention relates to multipass electric heaters of the character particularly suited for heating oil, water, and chemical liquids and solutions.

A purpose of the present invention is to construct a multipass electric heater more simply and economically, using standard shapes and components and largely avoiding the need for special dies.

A further purpose is to construct tubes of multipass electric heaters, referred to herein as heater chambers, which are more adequately braced against external pressure, and which do not require internal bracing by the electric heaters themselves in order to withstand the operating pressure. it is thus possible to withdraw and replace electric heater elements while the fluid is under pressure, and also to operate under much higher fluid pressures.

A further purpose is to arrange flow-conducting partitions and end ports in a manner to suit the desired velocity and volume of the fluid being heated, while making the construction of the heater chambers largely independent of the hydraulic features of the design.

A further purpose is to avoid the necessity of changing the Width and spacing of heater tubes in order to obtain variation in flow characteristics and in numbers of reverse flow passes.

A further purpose is to secure heat distribution from the electric heaters by radiation to the Walls of the heater chambers.

A further purpose is to have all of the heater chambers terminate at one end, and close the heater chambers at the other end, so that access to the heater chambers and the heaters can be obtained entirely at one terminal box, and wiring can be accomplished entirely at that end.

A further purpose is to permit access to the fluid passages at the end opposite to the terminal box for cleanout purposes, and avoid the difiiculties in constructing side cleanouts and maintaining such side cleanouts tight.

A further purpose is to avoid the necessity of disconnecting electric circuits in order to clean out fluid passages.

A further purpose is to simplify the construction of the heater when a cylindrical casing is required for high pressure operation.

A further purpose is to accomplish cooling inside the main casing and avoid the need for a separate cooler where successive heating and cooling are employed.

A further purpose is to save in size, weight and cost of constructing large multipass electric heaters.

A further purpose is to accomplish the construction of multipass electric heaters from cheap materials and structural shapes which are readily available in corrosion resisting alloys such as stainless steel commonly employed for such purposes.

Further purposes appear in the specification and in the claims.

In the drawings I have chosen to illustrate a few only of the numerous embodiments in which my invention nited States Patent 2,756,326 Fatented July 24, 1955 may appear, selecting the forms shown from the standpoint of convenience in illustration, satisfactory operation, and clear demonstration of the principles involved.

Figure 1 is a side elevation of one embodiment of the multipass electric heater of the present invention.

Figure 2 is a fragmentary enlarged plan section taken on the line 22 of Figure 3.

Figure is a fragmentary enlarged vertical section taken on the line 33 of Figure 2. The terminal box has been omitted in Figures 2 and 3.

Figure 4 is a fragmentary enlarged vertical transverse section taken on the line 4-4 of Figure 3.

Figure 5 is a fragmentary sectional perspective showing the connecting port and expansion joint at the closed end of the heater chamber.

Figure 6 is a fragmentary somewhat modified transverse section of the heater chamber showing heaters in place, but omitting the heater elements.

Figure 7 is an enlarged fragmentary plan view of the terminal end of an electric heater omitting the heater elements.

Figure 8 is a fragmentary longitudinal section of the heater chamber and electric heater at the terminal box.

Figure 9 is a partially broken side elevation of a modification of the multipass electric heater of the invention.

Figure 10 is a transverse section of the heater of Figure 9.

Figure 11 is a fragmentary top plan view showing a further modification.

Describing in illustration but not in limitation and referring to the drawings:

There are numerous applications in modern industry for electric multipass heaters, for heating fluids and especially liquids such as oils, water, chemical liquids and chemical solutions.

The attempt has been made in the past to produce such heaters by extending electric heaters through heater tubes disposed in a housing as required by the hydraulic conditions. Unfortunately, the requirements from the standpoint of velocity and volume of flow are widely variant, and this has necessitated production of a multiplicity of designs suited to special conditions, and adding to the cost because of the need in many instances for special components often produced by special dies.

In accordance with the present invention, it is possible to produce an effective multipass electric heater using inexpensive material and standard shapes which are readily available in corrosion resisting materials, such as stainless steel, frequently used 'in such construction. The need for special components and special dies is largely eliminated, and the construction of the entire heater chamber is made independent of the particular hydraulic requirements in regard to volume and velocitv of how within wide limits. 1

It is not necessary to change the width of heating tubes or the spacing of heating tubes with respect to one another in order to make various hydraulic designs.

In prior multipass electric heater construction, one of the difliculties has been the need to support the heater tubes against the fluid pressure, and in such prior designs it has frequently been necessary to brace the heater tubes internally by the electric heaters themselves, so that individual electric heaters could not be withdrawn when the hydraulic pressure was applied to the heater.

By the present invention internal bracing of the heater chamber is provided, so that much greater hydraulic pressures can be withstood, and it is not necessary to brace the heater chamber by the electric heater itself. Individual electric heaters can be removed for repair or inspection while the hydraulic pressure is still applied without danger of collapsing of the heater chamber.

Even for high pressure, a simple cylindrical construction with expansion joint inlet avoids the necessity for any special bracing of the heater housing.

One of the difliculties in the prior art has been the need for terminating the electric heaters at the opposite ends, and thus providing electric wiring conduit to both ends and also providing terminal boxes at both ends. In accordance with the present invention, the termination of the electric heater is provided entirely at one end, thus simplifying the terminal box construction and also avoiding the extra electric wiring.

The new construction also facilitates clean-out, since it is possible to clean out the fluid passages of the heater at the end opposite to the terminal box, and without disconnecting electric circuits for clean-out purposes. Side clean-outs formerly used can be avoided, and th s change is very desirable because it has been difficult in the past to keep side clean-outs tight and to construct suitable side clean-out arrangements.

In the new construction, reliance is no longer placed on uncertain contact of electric heaters with heater tubes for the purpose of heat transfer, but instead the heaters radiate to the heater chambers and thus transfer the heat.

The invention can conveniently be employed in installations which require successive heating and cooling. In fact, it is possible to add a cooling coil in the interior of an outer housing and thus save the need for a separate cooler.

The invention is particularly useful for large installations, where the saving in weight, size and expense are most marked.

Considering now the drawings in detail, the multipass electric heater of the invention includes a stack of spaced heater chambers 29, of which only two are shown, but it will be understood that any suitable number of such heater chambers will be employed. The heater chambers are desirably rectangular as shown, and are conveniently made of opposed angles 21 and 22 welded at 23 longitudinally at the opposite corners. The heater chambers are divided laterally and cross-braced against pressure by dividers 24 suitably welded to the outer Wall of the heater chamber. In the form shown in Figure 4, the dividers are channels while in the various forms of Figure 6, dividers 24' are angles. Here the dividers are suitably welded at 2.5 to one side wall of the heater chamber, and spot welded at 26 to the opposite wall. individual compartments 27 are provided for electric heaters which may be of any character well known in the art, but preferably as shown in Figures 6, 7 and 8 will be of the form of my copending application, Serial No. 303,549, filed August 12, 1952, for Electric Heater. in this form a heater bar 28 of steel or other suitable metal extends longitudinally of the heater and has at intervals lanced prongs 3b which engage in opposed recesses 31 at the end of insulators 32 spaced along the heater bar. The insulators may be of porcelain or other suitable material. The insulators have longitudinal openings 33 respectively in line which receive electric resistor elements 34 which are suitably wired, for example being cross connected at the closed end of the heater chamber. At the open end of the heater chamber the heater bars are suitably bolted at 35 to a terminal supporting lug 36 in the terminal box.

The insulator openings 33 desirably have longitudinal slots 37 along the sides of openings 33, which in the endmost insulator receive a metallic terminal 33 suitably of Monel, which is bolted at iii to the end of the electric resistor element and has an opening 41 to receive external wiring connections.

lt will be evident that at any time that it is desired, the terminal box can be opened up and the bolt 35 removed and the electric heater detached from the wiring and withdrawn for inspection. The cross-bracing by the partitions 24 guards against collapsing of the heater chamber under the pressure.

It will be understood that the number of heater pockets will vary according to the width of the heater chamber as desired.

The heater chambers are separated from one another, and from the housing at the endmost heater chambers, by spaces 42 which are longitudinally divided by partition 43 to form flues 44.

The heater chambers are closed by end walls 45 secured to the heater chambers as by welding, and this end 45 is spaced from the housing. The other end 46 of the heater chambers remains open into terminal box 47 which is closed by removable cover 43 and is provided with a conduit connection 50 to a junction box 51 which connects by conduit 52 with the source of electric power. It will be understood that the terminal box conduits and junction box will be hermetically sealed to make the structure explosion proof Where desired.

T he partition extends beyond the closed end :5 of the heater chamber as shown at 53 substantially to the end of the housing but terminates short of the housing at 54 at the opposite end (Figure 5) so as to provide a cross port 55 for reversal of horizontal flow of fluid between one flue 44 and the next flue 44. It will, of course, be understood that the number of flues t4 and the number of reversals in the space between any two heater chambers will depend upon the hydraulic arrangement and design.

The partition 43 as shown in the drawings is an angle, which is suitably united as by welding to one of the adjoining heater chamber walls, but is free at the other side so that relative adjustment can occur in expansion. On the other hand, since it engages the adjoining heater chamber wall or housing wall it provides support and bracing vertically.

The heater chambers and the fines adjoining them are surrounded by a preferably rectangular housing 56 suitably constructed of opposed angles 5'7 and 5S united as by welding at 68 at the corners. The end spaces between the heater chambers and the housing at the terminal box end are closed by end walls 61 suitably united by welding. At the other end the housing is flanged at 62 and receives a removable cover plate 63, suitably welded or bolted in place as desired, and permitting cleaning out of the fluid passages. The housing has inlet opening 64 desirably in the bottom near one side and an outlet opening 65 desirably at the top near the opposite side.

Each set of flues at a particular level communicates with the next set of flues by a connecting port 66. The connecting ports are staggered from level to level as best seen in Figure 4 so that the flow passes around the series of lines at one level, up through the connecting port to the next level and then around the series of flues at that level and up the connecting port to the next level. The communication between the levels at positions at which a connecting port is not desired is prevented by an expansion joint 67 which provides closure, support for the end of the heater chamber and adjustment under expansion and contraction. Thus the heater chamber is free from rigid attachment to the housing except at the terminal box end and floats and is supported by the expansion joint. The expansion joints desirably comprise channels 68 which extend clear across the housing immediately inside the removable cover 63 and secured as by welding at the end 70 to the housing, and telescoping and cooperating channels 71 facing in the same direction as the channel 63 and telescoping therewith and secured as by welding at "72 to the closed end of the heater chamber. The channel 71 extends across only to the edge of the port 66 which is suitably in line with the partition 43.

In operation, it will be evident that fluid to be heated will enter through inlet 64, will pass horizontally through flue 73, around end port 55 and back through flue 74, then up through cross-port 75, then back through flue '76, around end port 55, and forward through flue 77 and then up through cross-port 78 and back through flue 80,

around end port 55, then forward through flue 81 and out through outlet opening 65.

In some cases it is desired to surround the entire heater with a separate outer casing 82 as shown in Figures 9 and 10. In this case inlet may be provided at 83 through expansion joint 84 to inlet opening 64, and the fluid to be heated passed through the heater as already described and then out through outlet 65 which in this case is bent down at 85 to communicate with the space between the heater housing 56 and the outer casing 82. The fluid to be heated then is brought in heat transfer contact with the heat transfer coil 86 having inlet 87 and outlet 88, and finally passes out through the fluid outlet 90. The coil 86 may receive any suitable medium, such as cooling water or refrigerant, for example in an installation where it is desired to first heat and then cool the fluid.

In some cases it is desirable to provide special bracing of the heater housing 56, and this is accomplished by surrounding the housing with collars 91 suitably formed of channels and located at convenient spacing along the length. The collars are desirably welded directly to the housing for maximum support.

In the preferred embodiment, one of the collars at the rear is used as a control chamber, by closing the ends of a channel 92 at 93, and providing an outlet connection 65 which is on the opposite side of the heater from the outlet 65, so that fluid being heated in passing to the outlet passes longitudinally of the channel through a well 94 having a thermostatic control element 95 introduced through a pipe nipple and pressure fitting 96. Thus the fluid maintains contact with the thermostatic control element for the bulk of the length of the element.

In view of my invention .and disclosure variations and modifications to meet individual whim or particular need will doubtless become evident to others skilled in the art, to obtain all or part of the benefits of my invention without copying the structure shown, and I therefore, claim all such insofar as they fall within the reasonable spirit and scope of my claim.

Having thus described my invention what I claim as new. and desire to secure by Letters Patent is:

1. In a multipass electric heater, a stack of flat rectangular heater chambers in generally parallel relation spaced from one another, closed at one end and open at the other end, a housing surrounding the heater chamhers, inlet and outlet connections to the housing, there being flues in the spaces between the heater chambers,

6 partitions extending longitudinally of the fines part only of the distance to one end and separating the space between adjoining heater ch :mbers laterally into a plurality of fiues, there being a connecting port between a flue on one side of a given heater chamber and a corresponding flue on the other side of the given heater cham ber across the closed end of the heater chamber, electric heaters in the heater chambers, and a terminal box at the open end of the heater chambers.

2. A multipass electric heater according to claim 1, having an expansion joint between the closed end of each heater chamber and the housing at a lateral position on the heater chamber adjoining the connecting port.

3. A multipass electric heater according to claim 2, in which the expansion joint comprises cooperating channels interfitting with one another.

4. A multipass electric heater according to claim 2, in which the expansion joint comprises channels secured to the housing running fully across in spaced relation to the closed end of each heater chamber and cooperating channels secured at the closed end of each heater chamber and extending across to the edge of the connecting port.

5. A multipass electric heater according to claim 1, in which the partition is secured .to only one of the heater chambers and is free from but engaging the next heater chamber.

6. A multipass electric heater according to claim 1, in which the outer walls of the heater chamber comprise oppositely disposed .angles.

7. A multipass electric heater according to claim 1, in which the heater chambers are divided and cross supported by internal walls extending longitudinally.

8. A multipass electric heater according to claim 1, in combination with a collar surrounding the heater housing, and having a control well within the collar, there being a connection from the interior of the housing to the control well at one point and from the control Well to the outlet at a spaced position, and means for providing a thermostatic control element in the control well.

References Cited in the file of this patent UNITED STATES PATENTS 2,367,170 Fahrenwald Ian. 9, 1945 2,487,710 Hynes Nov. 8, 1949 2,489,205 Sweeney Nov. 22, 1949 2,530,799 Arvintz et al Nov. 21,1950 

